The present invention relates in general to valve control mechanisms for internal combustion engines, and more particularly to variable valve operating mechanisms for controlling valve timing, lift and duration in internal combustion engines.
Heretofore, many overhead valve and overhead cam mechanisms have been provided for operating the valves of internal combustion engines to control the opening and closing of the inlet and exhaust valves. In a more or less typical overhead valve and overhead cam layout, the valves are each operated by an associated rocker arm in a set and unvariable fashion. Adjustment of these, for the most part, has been to control the height of valve opening, usually referred to as the valve lift. Other mechanisms have been proposed for controlling the period or duration of valve opening without varying the valve lift.
A patent which typically depicts a mechanism for adjusting only the valve lift is U.S. Pat. No. 1,395,851 to F. B. McLean, wherein the lever or moment arm for opening of the valve is derived from a rocker arm that is pivotedly mounted intermediate its ends, and wherein the pivot point or fulcrum is shiftable to vary the amount of valve lift produced by the valve cam.
Another patent showing a mechanism that determines both the amount of valve lift and the time that the valve remains open is U.S. Pat. No. 2,412,457 to L. D. Harrison. This mechanism employs a profiled or specifically contoured adjusting rocker arm or lever that is shifted relative to the valve to be opened and closed. In this mechanism, the control of the lift and duration are integrated with each other and one cannot be realized in practice without affecting the other. The predominate change in this mechanism is in the duration, with the change in lift being very slight.
A number of U.S. patents have been more recently granted in the name of C. O. Burandt for various variable valve operating mechanisms involving two lever members for each valve. These include U.S. Pat. No. 4,414,931 granted Nov. 15, 1983, U.S. Pat. No. 4,459,946 granted July 17, 1984 and U.S. Pat. No. 4,484,546 granted Nov. 27, 1984.
Another prior patent involving a two lever control for each valve is U.S. Pat. No. 4,438,736 to Hara et al.
An object of the present invention is the provision of a variable valve operating mechanism involving a single rocker arm for each valve with a mechanism for positioning the rocker arm involving a pair of eccentrics to effect simultaneous change of valve lift and cam duration. My mechanism provides means to change valve timing, lift and duration by providing an eccentric shaft which is interrelated with an eccentric bushing so as to move the rocker arm for the associated valve in such manner as to change the leverage ratio or lift, and which changes valve timing by variation in the angle at which the cam contacts the rocker arm and varies the duration because of the shape of the rocker arm surface contacted by the cam.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.